diff options
Diffstat (limited to 'drivers/video/fb_ddc.c')
| -rw-r--r-- | drivers/video/fb_ddc.c | 116 |
1 files changed, 116 insertions, 0 deletions
diff --git a/drivers/video/fb_ddc.c b/drivers/video/fb_ddc.c new file mode 100644 index 000000000000..3aa6ebf68f17 --- /dev/null +++ b/drivers/video/fb_ddc.c @@ -0,0 +1,116 @@ +/* + * driver/vide/fb_ddc.c - DDC/EDID read support. + * + * Copyright (C) 2006 Dennis Munsie <dmunsie@cecropia.com> + * + * This file is subject to the terms and conditions of the GNU General Public + * License. See the file COPYING in the main directory of this archive + * for more details. + */ + +#include <linux/delay.h> +#include <linux/device.h> +#include <linux/fb.h> +#include <linux/i2c-algo-bit.h> + +#include "edid.h" + +#define DDC_ADDR 0x50 + +static unsigned char *fb_do_probe_ddc_edid(struct i2c_adapter *adapter) +{ + unsigned char start = 0x0; + struct i2c_msg msgs[] = { + { + .addr = DDC_ADDR, + .len = 1, + .buf = &start, + }, { + .addr = DDC_ADDR, + .flags = I2C_M_RD, + .len = EDID_LENGTH, + } + }; + unsigned char *buf; + + buf = kmalloc(EDID_LENGTH, GFP_KERNEL); + if (!buf) { + dev_warn(&adapter->dev, "unable to allocate memory for EDID " + "block.\n"); + return NULL; + } + msgs[1].buf = buf; + + if (i2c_transfer(adapter, msgs, 2) == 2) + return buf; + + dev_warn(&adapter->dev, "unable to read EDID block.\n"); + kfree(buf); + return NULL; +} + +unsigned char *fb_ddc_read(struct i2c_adapter *adapter) +{ + struct i2c_algo_bit_data *algo_data = adapter->algo_data; + unsigned char *edid = NULL; + int i, j; + + algo_data->setscl(algo_data->data, 1); + algo_data->setscl(algo_data->data, 0); + + for (i = 0; i < 3; i++) { + /* For some old monitors we need the + * following process to initialize/stop DDC + */ + algo_data->setsda(algo_data->data, 0); + msleep(13); + + algo_data->setscl(algo_data->data, 1); + for (j = 0; j < 5; j++) { + msleep(10); + if (algo_data->getscl(algo_data->data)) + break; + } + if (j == 5) + continue; + + algo_data->setsda(algo_data->data, 0); + msleep(15); + algo_data->setscl(algo_data->data, 0); + msleep(15); + algo_data->setsda(algo_data->data, 1); + msleep(15); + + /* Do the real work */ + edid = fb_do_probe_ddc_edid(adapter); + algo_data->setsda(algo_data->data, 0); + algo_data->setscl(algo_data->data, 0); + msleep(15); + + algo_data->setscl(algo_data->data, 1); + for (j = 0; j < 10; j++) { + msleep(10); + if (algo_data->getscl(algo_data->data)) + break; + } + + algo_data->setsda(algo_data->data, 1); + msleep(15); + algo_data->setscl(algo_data->data, 0); + if (edid) + break; + } + /* Release the DDC lines when done or the Apple Cinema HD display + * will switch off + */ + algo_data->setsda(algo_data->data, 0); + algo_data->setscl(algo_data->data, 0); + + return edid; +} + +EXPORT_SYMBOL_GPL(fb_ddc_read); + +MODULE_AUTHOR("Dennis Munsie <dmunsie@cecropia.com>"); +MODULE_DESCRIPTION("DDC/EDID reading support"); +MODULE_LICENSE("GPL"); |